feat: preserve isolated visitor agent runtime

tests/unit/core/test_security.py

@@ -55,6 +55,7 @@ def test_authenticate_visitor_token_returns_limited_anonymous_context() -> None:
     assert context.roles == ("visitor",)
     assert context.permissions == ("agent:run",)
     assert context.customer_ids == ()
+    assert context.data_scope == "public"
 
 
 def test_visitor_token_issuer_creates_short_lived_limited_token() -> None: